Clean air engines for transportation and other power applications

ABSTRACT

A low or no pollution engine is provided for delivering power for vehicles or other power applications. The engine has an air inlet which collects air from a surrounding environment. At least a portion of the nitrogen in the air is removed using a technique such as liquefaction, pressure swing adsorption or membrane based air separation. The remaining air is primarily oxygen, which is then compressed and routed to a gas generator. The gas generator has an igniter and inputs for the high pressure oxygen and a high pressure hydrogen containing fuel, such as hydrogen or methane. The fuel and oxygen are combusted within the gas generator, forming water and carbon dioxide with carbon containing fuels. Water is also delivered into the gas generator to control a temperature of the combustion products. The combustion products are then expanded through a power generating device, such as a turbine or piston expander to deliver output power for operation of a vehicle or other power uses. The combustion products, steam and, with carbon containing fuels, carbon dioxide, are then passed through a condenser where the steam is condensed and the carbon dioxide is collected or discharged. A portion of the water is discharged into the surrounding environment and the remainder is routed back to the gas generator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/533,611filed on Mar. 22, 2000, now U.S. Pat. No. 6,247,316, issued on Jun. 19,2001 which claims priority from copending Patent Cooperation Treaty(PCT) International Application No. PCT/US97/17006 filed on Sep. 22,1997 designating the United States; and is a continuation-in-part ofU.S. Pat. No. 5,680,764 filed on Jun. 7, 1995 and issued on Oct. 28,1997.

FIELD OF THE INVENTION

This invention contains environmentally clean engine designs that emitzero or very low pollutant levels during operation. The CLEAN AIR ENGINE(CLAIRE) invention is directly applicable to both transportation typevehicles including automobiles, trucks, trains, airplanes, ships and tostationary power generation applications. The designs feature hybrid,dual cycle and single cycle engines.

BACKGROUND OF THE INVENTION

The current art in generating power for transportation purposesbasically utilize the internal combustion gas or diesel engine. Thecurrent art for electric power generation utilize gas turbines and/orsteam turbines. These devices burn hydrocarbon fuels with air whichcontains (by weight) 23.1% oxygen, 75.6% nitrogen and the remaining 1.3%in other gases. The emissions resulting from the combustion of fuels forinternal combustion engines (gasoline or diesel), with air contain thefollowing pollutants that are considered damaging to our airenvironment. These smog causing pollutants, are: total organic gases(TOG); reactive organic gases (ROG); carbon monoxide (CO); oxides ofnitrogen (NOx); oxides of sulfur (SOx); and particulate matter (PM).Approximately one half of the total pollutants emitted by all sources ofair pollution in California are generated by road vehicles (EmissionInventory 1991, State of California Air Resources Board, preparedJanuary 1994). The major source of this vehicle pollution comes frompassenger cars and light to medium duty trucks.

No near term solutions appear in sight to drastically reduce the vastamount of air pollutants emitted by the many millions of automobiles andtrucks operating today. Based on the State of California Air ResourcesBoard study, the average discharge per person in California of the airpollutants from mobile vehicles, monitored by this agency during 1991and reported in 1994, was approximately 1.50 lb/day per person. With anationwide population of over 250,000,000 people, this data extrapolatesto over 180,000 tons of air borne emissions per day being discharged inthe USA by mobile vehicles. Also, the number of cars and miles that arebeing driven continue to increase, further hampering efforts to reducesmog causing pollutants.

Allowable emission thresholds are rapidly tightening by Federal andState mandates. These allowable emission reductions are placing severedemands on the transportation industry and the electric power generatingindustry to develop new and lower emission power systems.

Although considerable effort is being directed at improving the range ofelectric zero emission vehicles (ZEV) by developing higher energycapacity, lower cost storage batteries, the emission problem is beentransferred from the vehicle to the electric power generating plant,which is also being Federally mandated (Clean Air Act Amendments of1990) to reduce the same air toxic emissions as those specified forautomobiles and trucks.

The current world wide art of generating power for consumers ofelectricity depends primarily on fossil fuel burning engines. Theseengines burn hydrocarbon fuels with air. As described above, combustionof fossil fuels with air usually produce combustion products thatcontain a number of pollutants. Current Unites States regulatoryrequirements prescribe the amounts of the atmospheric pollutantspermitted in particular locations. Allowable pollutant thresholds aredecreasing over time and thereby putting more and more pressure onindustry to find better solutions to reduce these emissions ofpollutants in the electric power generating industry and other powergenerating industries.

Other energy sources being developed to solve the emissions problem, byexploiting non combustible energy sources include fuel cells and solarcells. Developers are solving many of the technological and economicproblems of these alternate sources. However, widespread use of theseenergy sources for vehicles and for electric power generating facilitiesdo not appear to yet be practical.

SUMMARY OF THE INVENTION

This invention provides a means for developing a zero or very lowpollution vehicle (ZPV) and other transportation power systems (i.e.rail and ship), as well as a zero or low pollution electric powergenerating facility. The zero or very low pollution is achieved byremoving the harmful pollutants from the incoming fuel and oxidizerreactants prior to mixing and burning them in a gas generator orcombustion chamber. Sulfur, sulfides and nitrogen are major pollutantsthat must be removed from the candidate fuels: hydrogen, methane,propane, purified natural gas, and light alcohols such as ethanol andmethanol. Since air contains 76% nitrogen by weight, it becomes a majorsource of pollution that also requires removal prior to combining itwith the clean fuel.

Cleansing of the fuel is straightforward and requires no furtherelaboration. The separation of the oxygen from the nitrogen in the air,however, is accomplished in a variety of ways. For instance, nitrogencan be removed from air by the liquefaction of air and gradualseparation of the two major constituents, oxygen and nitrogen, by meansof a rectifier (to be described later in more detail). The separation ofthe gases relies on the two distinct boiling points for oxygen (162° R)and for nitrogen (139° R) at atmospheric pressure. Air liquefies at anintermediate temperature of (142° R).

Other nitrogen removal techniques include vapor pressure swingadsorption, and membrane based air separation. With vapor pressure swingadsorption, materials are used which are capable of adsorption anddesorption of oxygen. With membrane based air separation, an air feedstream under pressure is passed over a membrane. The membrane allows onecomponent of the air to pass more rapidly there through than othercomponents, enriching the amount of different components on oppositesides of the membrane. Such membranes can be of a variety of differentmaterials and use several different physical processes to achieve thedesired separation of nitrogen out of the air.

One embodiment of this invention consists of a hybrid power system thatcombines a Rankine cycle thermal cycle with an auxiliary electric motorfor start-up and chill-down requirements. The thermal power cycle of theengine begins by compressing ambient air to high pressures, cooling theair during compression and during the expansion to liquid airtemperatures in a rectifier where separation of the oxygen and nitrogentakes place. The cold gaseous nitrogen generated is used to cool theincoming air and then is discharged to the atmosphere at near ambienttemperature. Simultaneously, the cold gaseous or liquid oxygen generatedby the rectifier is pressurized to gas generator pressure levels anddelivered to the gas generator at near ambient temperature. Fuel,gaseous or liquid, from a supply tank is pressurized to the pressurelevel of the oxygen and also delivered to the gas generator where thetwo reactants are combined at substantially the stoichiometric mixtureratio to achieve complete combustion and maximum temperature hot gases(6500° R). These hot gases are then diluted with water downstream in amixing section of the gas generator until the resulting temperature islowered to acceptable turbine inlet temperatures (2000° R).

The drive gas generated from this mixing process consists of high puritysteam, when using oxygen and hydrogen as the fuel, or a combination ofhigh purity steam and carbon dioxide (CO2), when using oxygen and lighthydrocarbon fuels (methane, propane, methanol, etc.). Following theexpansion of the hot gas in the turbine, which powers the vehicle or theelectric power generating plant, the steam or steam plus CO2 mixture arecooled in a condenser to near or below atmospheric pressure where thesteam condenses into water, thus completing a Rankine cycle.Approximately 75% of the condensed water is recirculated to the gasgenerator while the remainder is used for cooling and discharged to theatmosphere as warm water vapor. When using light hydrocarbons as thefuel, the gaseous carbon dioxide remaining in the condenser iscompressed to slightly above atmospheric pressure and either convertedto a solid or liquid state for periodic removal, or the gas can bedischarged into the atmosphere when such discharge is considerednon-harmful to the local air environment.

Since this thermal cycle requires time to cool the liquefactionequipment to steady state low temperatures, an electric motor, driven byan auxiliary battery, can be used to power the vehicle and initiate theRankine cycle until chill-down of the liquefaction equipment isachieved. When chill-down is complete the thermal Rankine engine,connected to an alternator, is used to power the vehicle or stationarypower plant and recharge the auxiliary battery.

The combination of these two power systems, also referred to as a hybridvehicle, emit zero or very low pollution in either mode of operation. Inaddition, the electric motor battery is charged by the zero or very lowpollution thermal Rankine cycle engine itself and thus does not requirea separate electric power generating plant for recharge. This reducesthe power demand from central power stations and also reduces apotential source of toxic air emissions.

In place of the electric drive motor and battery, the Rankine cycleengine, with the addition of a few control valves, can also be operatedas a minimally polluting open Brayton cycle, burning fuel and incomingair to power the vehicle during the period necessary to allow theRankine cycle engine liquefaction equipment time to chill-down. Thisfeature is another embodiment of this invention.

The zero or very low pollution Rankine cycle engine can also be used ina single cycle thermal mode for vehicles with long duration continuousduty such as heavy trucks, trains, ships and for stationary powergeneration plants where the chill-down time is not critical to theoverall operational cycle.

The adaptation of the Otto and Diesel thermal cycles to a low-pollutinghybrid engine are also included as embodiments of this invention. Byusing these thermal cycles, the need for a condenser and recirculatingwater system are eliminated. Low temperature steam or steam/carbondioxide gases are recirculated as the working fluid and thereforereplace the function of the recirculating water quench of the Rankinecycle embodiments previously discussed.

OBJECTS OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea low or zero pollution combustion based power generation system. Such asystem can be used in transportation and stationary power environments.Many countries' governments regulate the amount of pollution which canbe generated by power generation system. This invention addresses theneed for reduced pollution combustion based power generation systems.

Another object of this invention is to provide a high efficiencycombustion based power generation system.

Another object of the present invention is to provide a power generationsystem which can also produce water as a byproduct. In areas where wateris scarce the water byproducts produced by this invention areparticularly beneficial.

Another object of the present invention is to provide a combustion basedpower generation system which includes an air treatment plant forseparating nitrogen from the air prior to use of the air to combust ahydrocarbon fuel, such that nitrogen oxides are reduced or eliminated asbyproducts of combustion in the power generation system.

Other further objects of the present invention will become apparent froma careful reading of the included drawing figures, the claims anddetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustrating an embodiment of this invention andits elements, along with their connectivity. This embodiment constitutesa very low pollution or pollution-free hybrid power system for vehicularand other applications. The fuel reactant is a light hydrocarbon typesuch as methane propane, purified natural gas, and alcohols (i.e.methanol, ethanol).

FIG. 2 is a schematic illustrating an embodiment of this invention whichis also a very low pollution or pollution-free hybrid power system forvehicular and other applications where the fuel is gaseous hydrogen.

FIG. 3 is a schematic illustrating an embodiment of this invention whichis a very low pollution or pollution-free power system for vehicular andother applications during cruise and continuous duty. During start-upand a short period thereafter, the engine runs in an open Brayton cyclemode and thus emits some pollutants.

FIG. 4 is a plot of Temperature v. Entropy for the working fluidillustrating the first of two cycles used in the dual mode engine ofFIG. 3. This cycle is an open Brayton with inter-cooling betweencompressor stages (Mode I).

FIG. 5 is a plot of Temperature v. Entropy for the working fluidillustrating the second cycle used in the dual mode engine of FIG. 3.This cycle is a Rankine with regeneration, (Mode II).

FIG. 6 is a schematic illustrating an embodiment of this invention andits interconnecting elements. This embodiment constitutes a very lowpollution or pollution-free hybrid power system for vehicular and otherapplications similar to that of FIG. 1 but with the addition of tworeheaters to the power cycle for improved performance. The fuel reactantfor this cycle is a light hydrocarbon.

FIG. 7 is a schematic illustrating an embodiment of this invention andits interconnecting elements. This embodiment constitutes a very lowpollution or pollution-free hybrid power system similar to that of FIG.2 but with the addition of two reheaters to the power cycles forimproved performance. The fuel reactant for this cycle is hydrogen.

FIG. 8 is a plot of Temperature v. Entropy for the working fluid for thepower cycle used for the thermal engines shown in FIG. 6 and FIG. 7.This cycle features the Rankine cycle with regeneration and reheat forimproved performance.

FIG. 9 is a schematic illustrating an embodiment of this invention thatfeatures a very low pollution or non-polluting hybrid engine withelectric motor drive and a Rankine power cycle utilizing dynamic typeturbomachinery. The Rankine power cycle utilizes regeneration andreheaters for increased cycle efficiency and power density.

FIG. 10 is a schematic illustrating an embodiment of this invention thatfeatures a low polluting hybrid engine with an electric motor drive andan Otto power cycle reciprocating engine.

FIG. 11 is a schematic illustrating an embodiment of this invention thatfeatures a low polluting hybrid engine with an electric motor drive anda Diesel power cycle reciprocating engine.

FIG. 12 is a schematic illustrating a basic low-polluting engine where arectifier and air liquefaction devices of previous embodiments arereplaced with an air separation plant which separates nitrogen from airby any of a variety of techniques including liquefaction, vapor pressureswing adsorption, membrane based air separation, etc.

FIG. 13 is a schematic similar to that which is shown in FIG. 12 butincluding regeneration in the cycle disclosed therein.

FIG. 14 is a schematic similar to that which is disclosed in FIGS. 12and 13 except that a duel cycle arrangement is provided which features abottoming cycle for enhanced efficiency.

FIG. 15 is a schematic of a typical pressure swing adsorption plant foruse as the air separation plant in one of the engines disclosed in FIGS.12-14.

FIG. 16 is a schematic of a membrane flow two stage enrichment of oxygenand nitrogen system for use as part of the air separation plant of thecycles disclosed in FIGS. 12-14.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the first embodiment of the present invention, a zero orvery low pollution Rankine cycle thermal engine operating in parallelwith a zero emissions electric motor (also referred to as a hybridengine) is illustrated in FIG. 1. The Rankine engine consists of adynamic turbocompressor 10, a reciprocating engine 20, a powertransmission 30, a heat exchanger 40, a turboexpander 50, a rectifier60, a gas generator 70, a condenser 80, a recirculating water feed pump90, a water heater 100 and a condenser coolant radiator 110. Theelectric engine consists of an alternator 120, a battery 130 andelectric motor 140.

Hybrid engine operation begins by starting the electric motor 140 usingthe battery 130 as the energy source. The electric motor 140 drives thereciprocating engine 20 through the power transmission 30 and therebyinitiates the start of the thermal engine that requires a chill-downperiod for the liquefaction equipment consisting of heat exchanger 40,turboexpander 50 and rectifier 60.

Activation of the thermal engine initiates the compression of ambienttemperature air from a surrounding environment entering the dynamiccompressor 2 through an air inlet duct 1. The compressor 2 raises theair to the design discharge pressure. The air then exits through duct 3into intercooler 4 where the heat of compression is removed by externalcooling means 5 (i.e. air, water, Freon, etc.). Condensed water vaporfrom the air is tapped-off by drain 6. After the air exits intercooler 4through duct 7, at a temperature equal to the compressor inlet, itenters the reciprocating compressor 8 and is raised to the designdischarge pressure. The air exits through duct 9 into intercooler 11 andis again cooled to the inlet temperature of the compressor. Thiscompression/cooling cycle is repeated as the air exits intercooler 11through duct 12 and enters reciprocating compressor 13, then exitsthrough duct 14, enters intercooler 15 and exits through duct 16, tocomplete the air pressurization.

The high pressure, ambient temperature air then enters the scrubber 17where any gases or fluids that could freeze during the subsequentliquefaction are removed. These gases and liquids include carbon dioxide(duct 18 a and storage tank 18 b), oil (line 19 a and storage tank 19 b)and water vapor (tap off drain 21). The oil can be from a variety ofsources, such as leakage from the air compression machinery. The dry airthen exits through duct 22 and enters heat exchanger 40 where the air iscooled by returning low temperature gaseous nitrogen.

The dry air is now ready to pass through an air treatment device for theseparation of nitrogen out of the air and to provide nitrogen freeoxygen for combustion as discussed below. The dry air will contain, byweight, 23.1% oxygen, 75.6% nitrogen, 1.285% argon and small traces ofhydrogen, helium, neon, krypton and xenon (total of 0.0013%). Argon hasa liquefaction temperature of 157.5° R, which lies between the nitrogenand oxygen boiling points of 139.9° R and 162.4° R respectively.Therefore argon, which is not removed, will liquefy during theliquefaction process. The remaining traces of gases hydrogen, helium andneon are incondensable at temperatures above 49° R while krypton andxenon will liquefy; however, the trace amounts of these latter gases isconsidered insignificant to the following air liquefaction process.

The dry air then exits through duct 23 and enters the turboexpander 24where the air temperature is further reduced to near liquid airtemperature prior to exiting duct 25 and enters the rectifier 60 (a twocolumn type design is shown). Within the rectifier, if not before, theair is cooled to below the oxygen liquefaction temperature. Preferably,a two column type rectifier 60 is utilized such as that described indetail in the work: The Physical Principles of Gas Liquefaction and LowTemperature Rectification, Davies, first (published by Longmans, Greenand Co. 1949).

The air exits from the lower rectifier heat exchanger 26 through duct 27at liquid air temperature and enters the rectifier's lower column plateswhere the oxygen/nitrogen separation is initiated. Liquid with about 40%oxygen exits through duct 28 and enters the upper rectifier column wherea higher percentage oxygen concentration is generated. Liquid nitrogenat 96% purity is recirculated from the lower rectifier column to theupper column by means of duct 29. Gaseous nitrogen at 99% purity (1%argon) exits through duct 31 and enters heat exchanger 40 where coolingof the incoming air is performed prior to discharging through duct 32 tothe atmosphere at near ambient temperature and pressure. Gaseous orliquid oxygen at 95% purity (5% argon) exits through duct 33 and entersthe turboexpander compressor 34 where the oxygen is pressurized to thedesign pressure. The high pressure oxygen then exits through duct 35 andenters the gas generator 70.

A light hydrocarbon fuel (methane, propane, purified natural gas andlight alcohols such as ethanol and methanol) exits the fuel supply tank37 through duct 38 and enters the reciprocating engine cylinder 39 wherethe fuel is raised to the design discharge pressure. The fuel then exitsthrough duct 41 and enters the gas generator 70 to be mixed with theincoming oxygen at the stoichiometric mixture ratio to achieve completecombustion and maximum hot gas temperature (approximately 6500° R). Thegas generator includes an ignition device, such as a spark plug, toinitiate combustion. While the gas generator 70 is the preferred form offuel combustion device for this embodiment, other fuel combustiondevices could also be used, such as those discussed in the alternativeembodiments below. The products of combustion of these reactants resultin a high purity steam and carbon dioxide gas and a small amount ofgaseous argon (4%).

Following the complete combustion of the high temperature gases,recirculating water is injected into the gas generator 70 through line42 and dilutes the high temperature gases to a lower temperature drivegas acceptable to the reciprocating engine (approximately 2000° R). Thiswater influx also increases a mass flow rate of combustion productsavailable for expansion and power generation. The drive gas then exitsthe gas generator 70 through discharge duct 43, enters reciprocatingcylinder 44, expands and provides power to the power transmission 30.Other combustion product expansion devices can replace the reciprocatingcylinder 44, such as the dynamic turbines discussed in the sixthembodiment below. The gas exits through duct 45, enters the secondcylinder 46, expands and also provides power to the power transmission;the gas exits through duct 47 and powers the dynamic turbine 48 whichdrives the centrifugal compressor 2, which was driven by the electricmotor 140 during start-up, and the alternator 120 to recharge thebattery 130.

The gas then exits through duct 49, enters the water heater 100 whereresidual heat in the gas is transferred to the recirculating water beingpumped by pump 90, the water heater gas exits through duct 51, entersthe condenser 80 at near or below atmospheric pressure, wherecondensation of the steam into water and separation of the carbondioxide takes place. The condensed water exits through line 52, entersthe pump 90 where the pressure of the water is raised to the gasgenerator 70 supply pressure level. A major portion of the pump 90discharge water exits through line 53, enters the water heater 100 whereheat is transferred from the turbine 48 exhaust gas and then exitsthrough line 42 for delivery to the gas generator 70. The remainingwater from the discharge of pump 90 exits through duct 54 and is sprayedthrough nozzles 55 into radiator 110 (evaporative cooling). Coolant forthe condenser gases is recirculated through duct 56 to the radiator 110where heat is rejected to atmospheric air being pumped by fan 57.

The gaseous carbon dioxide, remaining after the condensation of thesteam, exits the condenser 80 through duct 58 and enters thereciprocating cylinder 59, (when the condenser pressure is belowatmospheric) compressed to slightly above atmospheric pressure anddischarged through duct 61. The compressed carbon dioxide can be storedin storage tank 62 and converted to a solid or liquid state for periodicremoval; or the gas can be discharged into the atmosphere when suchexpulsion is permitted.

It should be noted that this hybrid engine generates its own waterrequirements upon demand and thus eliminates the freezing problem of asteam Rankine cycle in a cold (below freezing) environment. Also, theengine generates its oxidizer requirements on demand and thus eliminatesmany safety concerns regarding oxygen storage.

A second embodiment of this invention, illustrated in FIG. 2, features ahybrid engine when using hydrogen in place of a hydrocarbon fuel. Whenusing hydrogen as the fuel no carbon dioxide is generated and only highpurity steam exits from the gas generator 70. Consequently all systemsrelated to carbon dioxide are deleted, and no other changes arebasically required. However, to maintain the same six cylinder engine ofFIG. 1, the hydrogen fuel FIG. 2 exits the fuel supply tank 37 throughduct 63, enters reciprocating engine cylinder 59, exits through duct 64,enters reciprocating engine cylinder 39, exits through duct 41 and isdelivered to the gas generator 70. This permits two stages ofcompression for the low density hydrogen.

A third embodiment of this invention, illustrated in FIG. 3, features adual cycle engine where a Brayton cycle is used for start-up andchill-down of the air liquefaction equipment (Mode I) and a Rankinecycle is used for cruise, idle and continuous duty (Mode II). Toincorporate this feature, high pressure air is tapped-off from cylinder13 (air pressurization as previously described for embodiment one) bymeans of bypass air duct 71 and modulated by valve 72. Also,recirculating water to the gas generator is modulated by means of valve73 to control the combustion temperature of the fuel and oxygen and theexit temperature of the gaseous mixture being delivered to power thecycle through duct 43.

The thermodynamic cycles for these two operating Modes are illustratedin FIG. 4 and FIG. 5. The working fluid for power cycle operation inMode I consists of steam, carbon dioxide and gaseous air. When operatingin Mode II the working fluid (as discussed in embodiment one and two)consists of steam and carbon dioxide when using hydrocarbon fuel andsteam only when using hydrogen.

An open Brayton cycle, illustrated in FIG. 4, with two stages ofintercooling the compressed air, 74 a, and 74 b, is used to power theengine during Mode I and initiates the chill-down of the liquefactionequipment for subsequent Mode II operation of the Rankine cycle withregeneration 75, illustrated in FIG. 5. Note that this embodimenteliminates the need for an electric motor, battery and alternator.

A fourth embodiment of this invention, illustrated in FIG. 6, includesall the elements of the first embodiment and adds two reheaters 150 and160 to improve the performance of this engine. While two reheaters 150,160 are shown, any number of reheaters can be utilized depending on therequirements of each specific application.

The engine operates as described for the first embodiment but with thefollowing changes. Hot gases exiting reciprocating cylinder 44 exitthrough duct 81, enter the reheater 150 where additional lighthydrocarbon fuel and oxygen is injected through ducts 88 and 89respectively. The heat of combustion of these reactants within thereheater 150 raises the incoming gas temperature to the level of the gasgenerator 70 output. The reheated gas then exits reheater 150 throughduct 82, enters reciprocating cylinder 46, expands and exits throughduct 83 and enters reheater 160 where additional oxygen and fuel isinjected. The heat of combustion of these reactants within the reheater160 again raises the incoming gas temperature to the same level as atthe gas generator 70 output. The heated gas then exits through duct 84and enters the dynamic turbine 48, as described previously in the firstembodiment. Fuel for the reheater 160 is supplied through duct 86. Theoxygen is supplied through duct 87.

A fifth embodiment of this invention, illustrated in FIG. 7, includesall the elements of the second embodiment and adds two reheaters 150 and160 to improve the performance. This engine operates as described forembodiment four except this engine uses hydrogen fuel. The Rankine cycleof these embodiments using regeneration and reheats is illustrated inFIG. 8. Regeneration is illustrated by 91 and the two reheats areillustrated by 92 a and 92 b.

A sixth embodiment of this invention; illustrated in FIG. 9, is similarto the fourth embodiment featuring reheaters, illustrated in FIG. 6,except all the machinery consists of dynamic type compressors andturbines. This type of machinery is more suitable for higher powerlevels (>1000 Shaft Horsepower (SHP)) required for rail, ship or standbypower systems.

The Rankine engine consists of dynamic turbocompressors 200, 210, and220, a power transmission 230, a heat exchanger 240, a turboexpander250, a rectifier 260, a gas generator 270, a first reheater 280, asecond reheater 290, a water heater 300, a condenser 310, arecirculating pump 320 and a condenser coolant radiator 330. Theelectric engine consists of an alternator 400, a battery 410 andelectric motor 420.

Engine operation begins by starting the electric motor 420 using thebattery 410 as the energy source. The electric motor 420 drives thedynamic compressor 201 through power transmission 230, andsimultaneously, valve 202 is opened and valve 203 is closed. Thisinitiates the start of the engine in a Brayton cycle mode. As enginespeed increases valve 202 is gradually closed and valve 203 is graduallyopened to slowly transition into the Rankine cycle mode and permit theliquefaction equipment to chill down. During this transitional periodthe electric motor 420 is used to maintain scheduled power and speeduntil steady state Rankine cycle conditions are achieved.

During thermal engine activation air enters turbocompressor 201 throughduct 204 and is raised to the design discharge pressure. The air thenexits through duct 205 into intercooler 206 where the heat ofcompression is removed by external cooling means 207 (i.e. air, water,Freon, etc.). Condensed water vapor is tapped-off by drain 208. Afterthe air exits intercooler 206 through duct 209 at a temperature equal tothe compressor inlet, it enters compressor 211 and is raised to thedesign discharge pressure. The air then exits through duct 212 intointercooler 213 and is again cooled to the inlet temperature of thecompressor 201. This compression/cooling cycle is repeated as the airexits intercooler 213 through duct 214, enters compressor 215, thenexits through duct 216, enters intercooler 217 and exits through duct218 to complete the air pressurization.

The high pressure ambient temperature air then enters scrubber 219 wheregases and fluids that are subject to freezing during the liquefactionprocess are removed (i.e. carbon dioxide, water vapor and oil). Carbondioxide exits through duct 221 a and is processed and stored inreservoir 221 b. Oil is drained through duct 222 a and stored inreservoir 222 b. Water vapor is drained through duct 223 and dischargedoverboard.

The dry air then exits through duct 224 and enters the heat exchanger240 where the air is cooled by returning gaseous nitrogen. It then exitsthrough duct 225 and enters turboexpander 226 where the air temperatureis further reduced to near liquid air temperature prior to exitingthrough duct 227 and enters the rectifier 260. The air exits from therectifier heat exchanger 228 through duct 229 at liquid air temperatureand enters the rectifier's lower column plates where oxygen/nitrogenseparation is initiated. Liquid with 40% oxygen exits through duct 231and enters the upper rectifier column where a higher percentage oxygenconcentration is generated. Liquid nitrogen at 96% purity isrecirculated from the lower rectifier column to the upper column bymeans of duct 232. Gaseous nitrogen at 99% purity (1% argon) exitsthrough duct 233 and enters the heat exchanger 240 where cooling theincoming dry air is performed prior to discharging through duct 234 tothe atmosphere at near ambient temperature and pressure. Gaseous oxygenor liquid oxygen at 95% purity (5% argon) exits through duct 235 andenters the turboexpander compressor 236 where the oxygen is pressurizedto the design pressure. The high pressure oxygen then exits through duct237 and enters the gas generator 270 through duct 238.

Fuel, i.e. methane, propane, purified natural gas and light alcoholssuch as methanol and ethanol, exits the fuel supply tank 239 throughduct 241 and enters the compressor 242 of turboexpander 250 and israised to the design discharge pressure. The pressurized fuel then exitsthrough duct 243 and enters the gas generator 270 through duct 244 whereit mixes with the incoming oxygen at stoichiometric mixture ratio toachieve complete combustion and maximum hot gas temperature(approximately 6500° R). The products of combustion of these reactantsresult in a high purity steam, carbon dioxide gas and a small amount ofgaseous argon (4%).

Following complete combustion of the high temperature gases,recirculating water is injected into the gas generator through line 245and dilutes the high temperature gases to a lower temperature drive gasacceptable to the dynamic turbine 247 (approximately 2000° R). The drivegas then exits the gas generator 270 through duct 246 and enters theturbine 247 of turbocompressor 220, where the gas expands and powers theair compressor 215 and the carbon dioxide compressor 273. The gas thenexits through duct 248 and enters reheater 280 where the heat extracteddue to the turbine 247 work is replenished. This heat is derived fromthe combustion of added fuel through duct 249 and added oxygen throughduct 251 into reheater 280.

The reheated gas then exits through duct 252 and enters turbine 253 ofturbocompressor 210 and expands to lower pressure. The power produced bythese expanding gases drive the alternator 400 and compressor 211, thenexhaust through duct 254 and enter reheater 290. The heat extracted fromthe gases resulting in the turbine work is replenished with the heat ofcombustion from added fuel through duct 255 and oxygen through duct 256.

The reheated gas then exits through duct 257, enters turbine 258 ofturbocompressor 200 and drives compressor 201 and power transmission230. The turbine exhaust gas then exits through duct 259 and enterswater heater 300 where the residual heat of the turbine 258 exhaust isused to preheat the water that is being recirculated to the gasgenerator 270. The gas then exits through duct 261, enters the condenser310 near or below atmospheric pressure, where condensation of the steaminto water and separation of the carbon dioxide gas occurs.

The condensed water exits through line 262, enters the pump 263 wherethe pressure is raised to the supply level of the gas generator 270. Amajor portion of the discharge water from pump 263 exits through line264, enters the water heater 300 where heat is absorbed from the turbineexhaust gas and then exists through line 245 for delivery to the gasgenerator 270. The remaining water from the discharge of pump 263 exitsthrough line 265 and is sprayed through nozzles 266 into radiator 330for evaporative cooling. Coolant for the condenser gas is recirculatedby pump 267 to the radiator 330 through line 268, where heat is rejectedto atmospheric air being pumped by fan 269.

The gaseous carbon dioxide, remaining from the condensation of steam,exits through duct 271 and enters compressor 273 of turbocompressor 220and is compressed to slightly above atmospheric pressure (when condenserpressure is below atmospheric) and discharged through duct 274 intostorage tank 275. The compressed carbon dioxide can be converted into aliquid or solid state for periodic removal, or the gas can be dischargedinto the atmosphere as local environmental laws permit.

The seventh embodiment of this invention, illustrated in FIG. 10,includes the liquefaction system of the previous embodiments bututilizes the intermittent but spontaneous combustion process of the Ottocycle as the thermal power engine. This embodiment eliminates the needfor the steam condenser and the recirculating water system.

The Otto cycle steam or steam/CO2 thermal engine consists of, inaddition to the liquefaction system previously described, a premixer 430where oxygen from duct 35, fuel from duct 41 and recirculating steam orsteam/CO2 from duct 301 are premixed in the approximate ratio of 20%, 5%and 75% by weight respectively. These premixed gases are then directedto the reciprocating pistons 302 through duct 303 and ducts 304 wherethey are compressed and ignited with a spark ignition system identicalto current Otto cycle engines. After the power stroke, the steam orsteam/CO2 gases are discharged to the dynamic turbine 48 through ducts305, 306 and then into duct 47. Some of the discharge gases are directedback to the premixer 430 through duct 301. The exhaust gases from thedynamic turbine 48 are then discharged to the atmosphere through duct307.

The eighth embodiment of this invention, illustrated in FIG. 11, issimilar to the seventh embodiment, except a Diesel power cycle is used.In this system a premixer 440 mixes the oxygen from duct 35 with steamor steam/CO2 from duct 308, at an approximate mixture ratio of 23% and77% by weight respectively, and discharges the gaseous mixture to thereciprocating pistons 309 through duct 311 and ducts 312 where themixture is compressed to a high pre-ignition temperature. The highpressure fuel, at approximately 5% of the total weight of the gasmixture in the piston cylinder, is injected through ducts 313 and burnsat approximately constant pressure. If necessary, an ignition device islocated within the combustion cylinder. The hot gases then rapidlyexpand as the piston moves to the bottom of its power stroke. Thesteam/CO2 gases are then discharged into ducts 313 and delivered to thedynamic turbine 48 through duct 47. Some of the discharged gases arediverted to the premixer 440 through the duct 308. The exhaust gasesfrom the dynamic turbine 48 are then discharged into the atmospherethrough duct 307.

FIG. 12 depicts a basic low-polluting engine 500 which conceptuallyrepresents many of the above-described first eight embodiments in a moresimplified manner. Rather than identifying specific machinery, FIG. 12depicts steps in the overall power production cycle. Additionally, theengine 500 of FIG. 12 replaces the rectifier and other liquefactionequipment of embodiments 1-8 with a more generalized air separationplant 530. Details of various different embodiments of this airseparation plant 530 are provided in FIGS. 15 and 16 and described indetail herein below.

The basic low-polluting engine 500 operates in the following manner. Airfrom a surrounding environment enters through an air inlet 510 into anair compressor 520. The air compressor 520 elevates the air enteringthrough the air inlet 510 and directs the compressed air to the airseparation plant 530. Various different air separation techniques can beutilized by the air separation plant 530 so that enriched nitrogen gasesexit the air separation plant 530 through an enriched nitrogen gasoutlet 532 and enriched oxygen gases exit the air separation plant 530through an enriched oxygen gases outlet 534. The enriched nitrogen gasesoutlet 532 typically returns back into the surrounding environment. Theenriched oxygen gases outlet 534 leads to the combustion device 550.

In the combustion device 550, the enriched oxygen gases from the airseparation plant 530 are combined with the hydrogen containing fuel froma fuel supply 540 and combustion is initiated within the combustiondevice 550. A water or carbon dioxide diluent is added into thecombustion device to decrease a temperature of the products ofcombustion within the combustion device 550 and to increase a mass flowrate for a steam or steam and carbon dioxide working fluid exiting thecombustion device 550.

This working fluid is then directed into an expander 560, such as aturbine. The turbine is coupled through a power transfer coupling 562 tothe air compressor 520 to drive the air compressor 520. FIG. 12 shows arotating shaft as one type of mechanical power transfer coupling 562.Another way to power the air compressor 520 is to generate electricityby means of the power absorber 570 and use part of the generatedelectricity to drive an electric motor which in turn powers the aircompressor 520. The expander 560 also is coupled through a powertransfer coupling 564 to a power absorber 570 such as an electricgenerator or a power transmission for a vehicle. The expander 560 isalso coupled through a power transfer coupling 566 to the air separationplant 530 to drive machinery within the air separation plant 530.

The working fluid is then discharged from the expander 560 through adischarge 572. The discharge 572 leads to a condenser 580. The condenserhas coolant passing through a coolant flow path 592 which causes waterportions of the working fluid entering the condenser 580 to becondensed. A water and carbon dioxide outlet 590 is provided for excesswater or water and carbon dioxide mixture from the condenser. A water orwater and carbon dioxide diluent path is also provided out of thecondenser 580 for returning water or water and carbon dioxide diluentback to the combustion device 550.

As should be readily apparent, the air compressor 520 is generallyanalogous to the turbocompressor 10 of the first embodiment. The airseparation plant 530 is generally analogous to the rectifier 60 of thefirst embodiment. The fuel supply 540 is generally analogous to the fuelsupply tank 37 of the first embodiment. The combustion device 550 isgenerally analogous to the gas generator 70 of the first embodiment. Theexpander 560 is generally analogous to the reciprocating cylinders 44,46 of the reciprocating engine 20 of the first embodiment. The powerabsorber 570 is generally analogous to the power transmission 30 of thefirst embodiment and the condenser 580 is generally analogous to thecondenser 80 of the first embodiment. Hence, the basic low-pollutingengine schematic of FIG. 12 represented by reference numeral 500 merelyprovides an overall depiction of the power production cycle of thisinvention. While a specific analogy has been drawn between this basiclow-polluting engine 500 and the first embodiment, shown in FIG. 1,similar analogies can be drawn to the other embodiments of thisinvention.

With particular reference to FIG. 13, details of a basic low-pollutingengine 600 featuring regeneration is provided. The low-polluting enginefeaturing regeneration 600 depicted in FIG. 13 is identical to the basiclow-polluting engine 500 of FIG. 12 except that handling of the workingfluid upon discharge from the expander 660 has been altered to featureregeneration. Specifically, the low-polluting engine featuringregeneration 600 includes an air inlet 610, air compressor 620, airseparation plant 630, fuel supply 640, combustion device 650, expander660 and power absorber 670 arranged similarly to the components 510,520, 530, 540, 550, 560, 570 of the basic low-polluting engine 500 shownin FIG. 12.

In contrast, the low-polluting engine featuring regeneration 600 directsthe working fluid through a discharge 672 which leads to a regenerator674. The working fluid exits the regenerator 674 through a regeneratoroutlet 676. The regenerator outlet 676 leads to a condenser 680. Withinthe condenser 680, the working fluid is cooled by action of a coolantflowing along a coolant flow path 682 to be separated into carbondioxide and water. The carbon dioxide exits the condenser 680 through acarbon dioxide outlet 684 and the water exits the condenser 680 throughthe water outlet 686. The water outlet 686 leads to a feed water pump688. Excess water is discharged from the engine 600 at a water excessoutlet 690. Other portions of the water are directed along a regeneratorwater flow path 692 through the regenerator 674 where the water ispreheated. The water or steam leaves the regenerator 674 along a waterdiluent path 694 leading back to the combustion device 650.

The carbon dioxide outlet 684 from the condenser 680 also leads into theregenerator 674 for preheating of the carbon dioxide. The carbon dioxideleaves the regenerator along a regenerator carbon dioxide flow 696 whichleads to a carbon dioxide compressor 697. The carbon dioxide compressor697 in turn leads to a carbon dioxide excess outlet 698 where excesscarbon dioxide is removed from the engine 600. If desired, a portion ofthe carbon dioxide can be directed along a carbon dioxide diluent path699 back to the combustion device 650 for use as a diluent within thecombustion device 650.

With particular reference to FIG. 14, a basic low-polluting engine 700with bottoming cycle is provided. As with the low-polluting enginefeaturing regeneration 600 of FIG. 13, portions of the low-pollutingengine featuring a bottoming cycle 700 are similar to the basiclow-polluting engine 500 of FIG. 12 up until discharge of the workingfluid from the expander 560. Hence, the low polluting engine featuring abottoming cycle 700 includes an air inlet 710, air compressor 720, airseparation plant 730, fuel supply 740, combustion device 750, expander760 and power absorber 770 having corresponding components in the engine500 of FIG. 12.

The working fluid is discharged from the expander 760 through adischarge 772 leading to a Heat Recovery Steam Generator(HRSG)/condenser 774. The working fluid is condensed and a water outlet775 directs water from the condenser 774 and a carbon dioxide outlet 776directs carbon dioxide from the condenser 774. The carbon dioxide outlet776 leads to a carbon dioxide compressor 777, a carbon dioxide excessoutlet 778 and carbon dioxide diluent path 779 leading back to thecombustion device 750.

The water outlet 775 leads to a feed water pump 780 which in turn leadsto a water excess outlet 781 and a water regeneration path 782 where thewater is regenerated within a bottoming regenerator 787. The water exitsthe bottoming regenerator 787 along a water diluent path 783 leadingback to the combustion device 750.

The HRSG/condenser 774 and regenerator 787 are driven by a bottomingcycle including a bottoming cycle boiler 784 which boils water in thebottoming cycle from the discharge working fluid from the discharge 772and entering the HRSG/condenser 774. The topping cycle also includes abottoming turbine 786 and a bottoming regenerator 787 which cools steamexiting the steam turbine 786 and heats water entering the water diluentpath 783. The bottoming cycle also includes a bottoming condenser 788cooled by a coolant within a coolant line 789. Hence, the working fluidsuch as water within the bottoming cycle passes from the condenser 788to the boiler 784 where the working fluid is heated and turned into agas. Note that the HRSG/condenser 774 and boiler 784 are integratedtogether but that only heat exchange is allowed, not mixing. Thebottoming cycle working fluid then passes through the turbine 786 forproduction of power which can be directed to the power absorber 770 orother components of the low-polluting engine featuring a bottoming cycle700. The working fluid then exits the turbine 786 and is cooled in theregenerator 787 before returning to the condenser 788.

The air separation plants 530, 630, 730 of FIGS. 12-14 can be any of avariety of different apparatuses or systems which are capable ofremoving at least a portion of the nitrogen from air. For instance, andspecifically discussed above with respect to the first through eighthembodiments of FIGS. 1-11, the air separation plant 530, 630, 730 caninclude a rectifier such as the rectifier 60 of FIG. 1 or otherliquefaction equipment which separate nitrogen from the air byliquefaction.

However, liquefaction processes are not the only processes that canremove at least a portion of nitrogen from air. Several other processesare available to achieve this goal. These processes, which are describedin detail below, can be substituted for the cryogenic liquefactionprocess described in detail hereinabove. One alternative techniqueavailable for use in the air separation plant 530, 630, 730 is apressure swing adsorption plant 800 (FIG. 15). The pressure swingadsorption process, also called vacuum pressure swing adsorption, usesmaterials which are capable of adsorption and desorption of oxygen ornitrogen such as, for example, synthetic zeolites. The vacuum pressureswing adsorption process can be used to separate oxygen and nitrogenfrom air.

The process typically employs two beds that go through swings inpressure from above atmospheric to below atmospheric pressure. Each bedcycles sequentially from adsorption to desorption and regeneration andback to adsorption. The two beds operate in a staggered arrangement inwhich one bed is adsorbing while the other bed is regenerating. Thus thebeds alternately produce a gaseous product of high oxygen content. Withthis process, a gaseous mixture can be produced with a wide range ofoxygen purities. As an example, oxygen purities ranging from 90% to 94%are used in many industrial applications and can be successfullyproduced with commercially available vacuum pressure swing adsorptionprocesses such as those produced by Praxair, Inc. with worldheadquarters located at 39 Old Ridgebury Road, Danbury, Conn.06810-5113.

With particular reference to FIG. 15, a layout of a typical pressureswing adsorption plant 800 is shown. Initially, the air inlet 510 andfeed compressor 520 are provided analogous to the air inlet 510 and aircompressor 520 of the basic low-polluting engine schematic 500 shown inFIG. 12. Preferably, a filter 515 is interposed between the air inletand the feed compressor to filter particulates out of the air inletstream. The compressed air discharged from the feed compressor 520 isdirected to a first inlet line 810 passing through a first inlet linevalve 815 and into a first enclosure 820.

The first enclosure 820 is provided with an appropriate material capableof adsorption and desorption of oxygen or nitrogen. One material that isused in these applications is zeolite. Two outlets are provided from thefirst enclosure 820 including a first oxygen outlet 830 coupled to thefirst enclosure 820 through a first valve 832 and a first nitrogenoutlet 835 coupled to the first enclosure 820 through a first nitrogenvalve 836. The first nitrogen outlet 835 leads to a nitrogen compressor837 which raises the gases in the first nitrogen outlet 835 back toatmospheric pressure for discharge through nitrogen discharge 839. Infact, the first nitrogen outlet 835 and first oxygen outlet 830 do notcontain pure oxygen or nitrogen but rather merely gases which areenriched in content with oxygen or nitrogen.

The first oxygen outlet 830 leads to a surge tank 870 with a valve 875beyond the surge tank 870 and leading to an oxygen supply line 880. Inparallel with the first enclosure 820, a second enclosure 850 isprovided. The second enclosure 850 is similarly loaded with anappropriate material capable of adsorption and desorption of oxygen ornitrogen. A second inlet line 840 leads from the feed compressor 520through a second inlet line valve 845 and into the second enclosure 850.A second oxygen outlet 860 leads out of the second enclosure 850 and onto the surge tank 870 through a second oxygen outlet valve 862. A secondnitrogen outlet 865 also leads out of the second enclosure 850 through asecond nitrogen outlet valve 866 and on to the compressor 837. A cyclecontroller 890 controls the opening and closing of the various valves815, 832, 836, 845, 862, 866 and 875.

One typical operation sequence of the pressure swing adsorption plant800 is as follows. Initially, all of the valves are closed except forthe first nitrogen valve 836 and the nitrogen compressor 837 is used toreduce pressure in the first enclosure 820 to below atmosphericpressure. The first nitrogen valve 836 is then closed. Next, the firstinlet valve 815 is opened. With the first inlet line valve 815 open andall other valves closed, the feed compressor directs air into the firstenclosure 820.

As pressure builds up within the first enclosure 820, the materialwithin the first enclosure 820 is caused to adsorb different moleculeswithin the air in a discriminate fashion. For instance, the material canbe selected to adsorb nitrogen at elevated pressure. At reducedpressure, the adsorption effect reverses to desorption.

In essence, if the material adsorbs nitrogen at pressures elevated aboveatmospheric pressure and desorbs nitrogen at pressures below atmosphericpressure, the various valves 815, 832, 836 and 875 are sequentiallyoperated so that the first enclosure 820 has an elevated pressure andadsorbs nitrogen before the remaining enriched oxygen air is allowed tofreely flow out of the first enclosure 820 along the first oxygen outlet830. When the oxygen enclosure 820 has a pressure below atmosphericpressure, the material within the first enclosure 820 is desorbing thenitrogen while the first nitrogen outlet valve 836 is open. In this way,when nitrogen is being adsorbed, the remaining air within the firstenclosure 820 is enriched in oxygen and is directed to the first oxygenoutlet 830 and when the material within the enclosure 820 is desorbingthe nitrogen, the nitrogen enriched gases within the first enclosure 820are allowed to flow into the first nitrogen outlet 835 and to thenitrogen discharge 839.

The zeolite material within the enclosure 820 benefits from someresidence time to adsorb as much nitrogen (or oxygen) as desired. Duringthis time no oxygen rich or nitrogen rich gases flow to the oxygensupply line 880 or the nitrogen discharge 839. Hence, it is beneficialto use a second enclosure 850 similar to the first enclosure 820 whilethe valves 815, 832 and 836 are all closed and the zeolite material inthe first enclosure 820 is adsorbing nitrogen (or oxygen).

Specifically the valves 845, 862 and 866 are sequentially opened andclosed to cause the second enclosure 850 to operate in a manner similarto that outlined with reference to the first enclosure 820 above. Whenthe material within the second enclosure 850 is adsorbing nitrogen (oroxygen) the process is reversed so that the first enclosure 820, havinghad its zeolite material appropriately desorbed, is brought back on linefor repetition of the alternating pattern of use between the firstenclosure 820 and the second enclosure 850. As should be apparent,additional enclosures besides the first enclosure 820 and secondenclosure 850 could be utilized if the adsorbing material requires moreresidence time or to increase the overall throughput of oxygen enrichedgases from the air. Over time, the material within the first enclosure820 which adsorbs and desorbs the oxygen or nitrogen tends to lose itseffectiveness. The material can be regenerated, if it is in the form ofa synthetic zeolite, by application of heat or other regeneration means.Accordingly, when the material within the first enclosure 820 begins tolose its effectiveness, such a heat treatment can be performed or thezeolite material replaced. Should the adsorbing material be configuredto adsorb and desorb oxygen rather than nitrogen, the above describedoperation of the pressure swing adsorption plant 800 would be adjustedto provide the desired separation of oxygen from nitrogen.

With particular reference to FIG. 16, details of an alternativeapparatus and system for use within the air separation plants 530, 630,730 is provided. In such membrane-based air separation systems 900 theseparation of air into its components is achieved by passing an air feedstream under pressure over a membrane. The pressure gradient across themembrane causes the most permeable component to pass through themembrane more rapidly than other components, thereby creating a productstream that is enriched in this component while the feed stream isdepleted in this component.

The transport of the air through a membrane can follow several physicalprocesses. As an example, these processes could be: 1) Knudsen flowseparation which is based on molecular weight differences between thegases; 2) Ultramicroporous molecular sieving separation; and 3)Solution-diffusion separation which is based both on solubility andmobility factors. In the case of a solution-diffusion process the airfirst dissolves in a polymer, then diffuses through its thickness andthen evaporates from the other side into the product stream.

Several types of membranes are available for this process, each havingspecific advantages in particular situations. For example, celluloseacetate membranes exhibit good separation factors for oxygen andnitrogen, but have low flux rates. Thin film composite membranes placedover microporous polysulfone exhibits lower separation factors thancellulose acetate, but have a higher flux at the same pressuredifferential. Repeating the process in a series configuration canincrease the oxygen concentration in the product stream. For example,one industrial membrane, in two passes, may enrich the oxygen content ofair to about 50%.

The above described membrane processes operate at a temperature that isnear ambient temperature. A higher-than-ambient temperature may arise asa result of a possible temperature rise resulting from pressurization ofthe air feed stream to create a pressure difference across the membrane.

Still another membrane separation process uses an electroceramicmembrane. Electroceramics are ionic solid solutions that permit movementof ions. To become appreciably mobile, the oxide ion, because of itssize and charge, requires a high temperature (about 800° F.) to overcomethe solid oxide lattice energy. The electroceramic membrane processintegrates well with the production of power described in this inventionbecause the power generating process produces waste heat that can beused to generate the required operating temperature of the membrane. Forinstance, and with reference to FIG. 12, the expander 560 and gasgenerator 550 can be configured such that the working fluid exiting theexpander 560 at the discharge 572 has a temperature at or above 800° F.The working fluid can then be routed to a heat exchanger which heats theelectroceramic membranes to 800° F. for use in the air developmentsystem 530.

The oxygen ions move through the lattice because of a gradient inpressure across the membrane. On the high oxygen partial pressure sideof the membrane, oxygen is reduced when it receives four electrons andoccupies two vacancies. At the low oxygen partial pressure side,vacancies are created by the reverse reaction. Oxide ions at the lowpartial pressure side can be removed by liberation of oxygen. The rateof diffusion through the membrane is determined by ion mobility. Thismobility is a characteristic of a particular material, and is dependenton the size, charge and geometry of the cations in the lattice. Apossible material for formation of the electroceramic membrane is yttriastabilized zirconia.

With particular reference to FIG. 16, one arrangement for the membranebased air separation system for use in the air separation plants 530,630, 730 is depicted by reference numeral 900. In this embodiment forthe air separation plant, an air inlet 510 and feed compressor 520 areprovided similar to the air inlet 510 and feed compressor 520 disclosedin FIG. 12 with regard to the basic low-polluting engine 500. Thecompressed air is then directed to a junction 910 where return flowsfrom various membrane chambers return for reprocessing and are combinedtogether within the junction 910. A junction outlet 915 provides theonly outlet from the junction 910. The junction outlet 915 leads to afirst membrane enclosure 920.

The first membrane enclosure 920 is preferably an enclosure which has aninlet and a membrane dividing the enclosure into two regions. Twooutlets are provided in the enclosure. One of the outlets is on the sameside of the membrane as the inlet and the other outlet is located on aside of the membrane opposite the inlet. If the membrane is of a typewhich allows oxygen to pass more readily there through than nitrogen, anoxygen rich outlet 924 is located on the downstream side of the membraneand a nitrogen rich outlet 926 is located on a same side of the membraneas the inlet 915. If the membrane allows nitrogen to pass more readilythere through, the arrangement of the outlets is reversed.

The junction outlet 915 passes into the first membrane enclosure 920through the inlet in the first membrane enclosure 920. Because oxygenflows more readily through the membrane within the first membraneenclosure 920, gases flowing through the oxygen rich outlet 924 have anincreased percentage of oxygen with respect to standard atmosphericoxygen percentages and the nitrogen rich outlet 926 has a nitrogencontent which is greater than that of standard atmospheric conditions.

The oxygen rich outlet 924 leads to a second membrane enclosure 930where it enters the second membrane enclosure 930 through an oxygen richinlet 932. The second membrane enclosure 930 is arranged similarly tothe first membrane enclosure 920. Hence, a membrane is provided withinthe second membrane enclosure 930 and two outlets are provided includingan oxygen super rich outlet 934 on a side of the membrane opposite theoxygen rich inlet 932 and a second outlet 938 located on a common sideof the membrane within the second membrane enclosure 930 as the oxygenrich inlet 932.

The oxygen super rich outlet 934 leads to an oxygen supply 936 for usewithin one of the engines 500, 600, 700 discussed above. The gasesflowing through the second outlet 938 typically have oxygen and nitrogencontents matching that of standard atmospheric conditions butmaintaining an elevated pressure. The second outlet 938 returns back tothe junction 910 for combining with air exiting the feed compressor 520and for repassing through the first membrane enclosure 920 as discussedabove.

The nitrogen rich outlet 926 exiting the first membrane enclosure 920 ispassed to a third membrane enclosure 940 where it enters the thirdmembrane enclosure 940 through a nitrogen rich inlet 942. The thirdmembrane enclosure 940 is similarly arranged to the first membraneenclosure 920 and second membrane enclosure 930 such that a membrane islocated within the third membrane enclosure 940 and two outlets areprovided from the third membrane enclosure 940. One of the outlets is anitrogen super rich outlet 944 on a side of the membrane within thethird membrane enclosure 940 similar to that of the nitrogen rich inlet942. The nitrogen super rich outlet 944 can lead to a surroundingatmosphere or be used for processes where a high nitrogen content gas isdesirable.

A third permeate return 948 provides an outlet from the third membraneenclosure 940 which is on a side of the membrane within the thirdmembrane enclosure 940 opposite the location of the nitrogen rich inlet942. The third permeate return 948 leads back to the junction 910 forreprocessing of the still pressurized air exiting the third membraneenclosure 940 through the third permeate return 948. This air passingthrough the third permeate return 948 is typically similar in content tothe second permeate return 938 and the air exiting the feed compressor520.

While many different types of membranes can be utilized within the firstmembrane enclosure 920, second membrane enclosure 930 and third membraneenclosure 940, the type of membrane would typically not alter thegeneral arrangement of the membrane enclosures 920, 930, 940 andconduits for directing gases between the various permeates 920, 930, 940and other components of the membrane based air separation plant 900 ofFIG. 16.

While various different techniques have been disclosed for separation ofnitrogen and oxygen from air, this description is not provided toidentify every possible air separation process or apparatus. Forexample, economic and other consideration may make application ofcombinations of the above described processes advantageous. Rather,these examples are presented to indicate that several separationprocesses are available to accomplish the goal of enriching the oxygencontent of air supplied to a combustion device and decreasing acorresponding nitrogen content of the air supply to a combustion device.By reducing an amount of nitrogen passing into a combustion device suchas these combustion devices 550, 650, 750, an amount of nitrogen oxidesproduced as products of combustion within the combustion device 550,650, 750 is reduced and low-pollution combustion based power productionresults.

Moreover, having thus described the invention it should now be apparentthat various different modifications could be resorted to withoutdeparting from the scope of the invention as disclosed herein and asidentified in the included claims. The above description is provided todisclose the best mode for practicing this invention and to enable oneskilled in the art to practice this invention but should not beconstrued to limit the scope of the invention disclosed herein.

What is claimed is:
 1. A low or no pollution emitting combustion engineto provide power for various applications such as vehicle propulsion orstationary electric power generation, the engine comprising incombination: an air inlet; a source of fuel at least partially includinghydrogen; an air separator including an inlet coupled to said air inlet,said air separator configured to remove nitrogen from the air enteringsaid air inlet so that remaining air is primarily oxygen and with othernon-oxygen constituents, and an oxygen enriched air outlet; a fuelcombustor, said fuel combustor receiving fuel from said source of fueland oxygen from said oxygen enriched air outlet of said air separator,said combustor combusting said fuel with said oxygen to produce elevatedpressure and elevated temperature combustion products including steam,said combustor having a discharge for said combustion products; whereinat least part of a non-steam portion of the combustion products isremoved from the combustion products after discharge from saidcombustor, so that the combustion products have more steam than thecombustion products at said discharge; and a return line for routing atleast a portion of the steam rich combustion products back to saidcombustor.
 2. The engine of claim 1 wherein said air separator includesmeans to liquefy at least a portion of the air and means to separateliquid portions of the air from non-liquid portions of the air and meansto direct portions of the air which have a greater oxygen content tosaid oxygen rich outlet.
 3. The engine of claim 1 wherein at least onecompressor is oriented between said air inlet and said air separator,raising a pressure of the air; wherein at least one intercooler isoriented between a first said compressor and said air separator, said atleast one intercooler reducing a temperature of the air passing therethrough; and wherein said air separator includes an expander downstreamfrom said at least one intercooler, said expander reducing a pressure ofthe air and a temperature of the air to below a condensation point ofthe oxygen within the air, said air separator including said oxygenenriched air outlet.
 4. The engine of claim 1 wherein said air separatorincludes a material capable of adsorption and desorption of an airconstituent gas, said material located in contact with air from said airinlet.
 5. The engine of claim 4 wherein said material adsorbs nitrogenand desorbs nitrogen based on pressure of the air adjacent the material,wherein at least two separate beds of material are provided with meansto sequentially increase and decrease pressure adjacent said beds ofmaterial to be above atmospheric pressure and below atmosphericpressure, said beds including means to selectively discharge airenriched with oxygen out of said beds and to said oxygen enriched airoutlet.
 6. The engine of claim 1 wherein said air separator includes atleast one membrane, said membrane having a different permeability foroxygen than for nitrogen, said air separator directing air adjacent oneside of said membrane and collecting oxygen rich gases and nitrogen richgases from opposite sides of said membrane, the oxygen rich gasesdirected to said oxygen enriched air outlet of said air separator. 7.The engine of claim 6 wherein two or more membranes are arranged suchthat air flow through said membranes occurs in series and greater oxygenenrichment and nitrogen enrichment are achieved.
 8. The engine of claim7 wherein a feed compressor is coupled to said air inlet including meansto increase pressure of air entering said air separator to aboveatmospheric pressure, said membrane being more permeable to oxygen thanto nitrogen, said membrane juxtaposed between an outlet of said feedcompressor and said oxygen rich outlet, and a second membrane juxtaposedbetween said oxygen rich outlet and an oxygen super rich outlet, suchthat gases on a side of said second membrane opposite said oxygen richoutlet have a greater percentage of oxygen than on said oxygen richoutlet side of said second membrane, said oxygen super rich outletleading to said oxygen enriched air outlet of said air separator.
 9. Theengine of claim 1 wherein said air separator includes an electroceramicmembrane juxtaposed between said air inlet and said oxygen enrichedoutlet, said electroceramic membrane including an ionic solid solutionwhich permits movement of oxygen ions there through.
 10. The engine ofclaim 1 wherein a combustion product expander is coupled to saiddischarge of said combustor, said expander configured to output powerfrom said engine and an exhaust for the combustion products, whereinsaid exhaust is coupled to a means to return at least a portion of thecombustion products back to said combustion device, such that saidengine operates as an at least partially closed cycle.
 11. The engine ofclaim 10 wherein said means to return the combustion products back tosaid combustion device includes means to cool the combustion productswhile exchanging heat with a separate working fluid upstream from aturbine in a separate closed Rankine cycle engine.
 12. The engine ofclaim 1 wherein a combustion products expander is coupled to saiddischarge of said combustor, said expander outputting power from saidengine and having an exhaust for the combustion products.
 13. The engineof claim 12 wherein a reheater is located downstream of said combustionproduct expander, said reheater enhancing a temperature of saidcombustion products exiting said combustion product expander.
 14. A lowor no pollution emitting combustion engine to provide power for variousapplications such as vehicle propulsion, the engine comprising incombination: an air inlet configured to receive air from an environmentsurrounding said engine; a source of fuel at least partially includinghydrogen; an air separator including an inlet coupled to said air inlet,said air separator configured to remove nitrogen from the air enteringsaid air inlet so that remaining air is primarily oxygen and with othernon-oxygen constituents, and an oxygen enriched air outlet; a fuelcombustor, said fuel combustor receiving fuel from said source of fueland oxygen from said oxygen enriched air outlet of said air separator,said combustor combusting the fuel with the oxygen to produce elevatedpressure and elevated temperature combustion products including steam,the combustor having a discharge for the combustion products; acombustion products expander downstream from said discharge of saidcombustor, said expander outputting power from said engine and having anexhaust for the combustion products; and a reheater is locateddownstream of said combustion product expander, said reheater enhancinga temperature of said combustion products exiting said combustionproduct expander.
 15. The engine of claim 14 wherein said engineincludes a means to compress the oxygen and the fuel before the oxygenand the fuel enter said combustion device.
 16. The engine of claim 15wherein said means to compress the oxygen includes at least twocompressors, each said compressor including an intercooler therebetween, at least two of said compressors oriented between said airinlet and said air treatment device, such that the oxygen is compressedalong with other constituents of the air entering the air inlet.
 17. Theengine of claim 14 wherein said combustion device includes a waterinlet, said water inlet configured to receive water from at least onesource which includes water originally created as one of said combustionproducts exiting said combustion chamber, said water inlet placing waterinto contact with said combustion products for mixing with saidcombustion products and output through said discharge of said combustiondevice, whereby a temperature of gases exiting said combustion devicethrough said discharge is decreased and a mass flow rate of gasesexiting said combustion device through said discharge is increased. 18.The engine of claim 17 wherein at least a portion of said combustionproducts exiting said exhaust of said combustion product expansiondevice are routed to a condenser where the steam within said combustionproducts is condensed to water, said condenser including a return ductto said water inlet of said combustion device, whereby the steam/wateracts as a working fluid for a Rankine cycle.
 19. The engine of claim 14wherein a bypass air duct is provided between said air inlet and saidcombustion device, said bypass air duct delivering air, includingnitrogen, to said combustion device, said bypass air duct including avalve capable of blocking said bypass air duct, whereby air, includingnitrogen, can be provided to the combustion device when desired.
 20. Theengine of claim 15 wherein each of said means to compress is coupled toan electric motor and battery such that said electric motor and batterycan drive said means to compress for compression of the oxygen, andwherein said means to compress is also coupled to at least one expanderin fluid communication with said combustion products exiting saiddischarge of said combustion device, such that said expanders can drivesaid means to compress for compression of the oxygen; and wherein saidelectric motors include means to charge said battery when said expandersdeliver excess power beyond that necessary to drive said means tocompress for compression of the oxygen.
 21. The engine of claim 14wherein at least one compressor is oriented between said air inlet andsaid air separator, raising a pressure of the air; wherein at least oneintercooler is oriented between a first said compressor and said airseparator, each said intercooler reducing a temperature of the airpassing there through; and wherein said air separator includes anexpander downstream from a last said intercooler, said expander reducinga pressure of the air and a temperature of the air to below acondensation point of the oxygen within the air, said air separatorincluding said oxygen enriched air outlet substantially free ofnitrogen.
 22. The engine of claim 21 wherein said air separator includesa nitrogen outlet, and wherein said engine includes a heat transferdevice including means to transfer heat between nitrogen exiting saidair separator through said nitrogen outlet and air between said expanderand said air inlet.
 23. The engine of claim 21 wherein said expander iscoupled to an oxygen compressor interposed between said oxygen enrichedair outlet of said air separator and said combustion device, whereby apressure of the oxygen is increased.
 24. The engine of claim 21 whereina scrubber is provided between said air separator and said air inlet toremove gases capable of freezing from the air.
 25. The engine of claim22 wherein said air separator includes a two column rectifier downstreamfrom said expander, said rectifier including said oxygen enriched airoutlet and said nitrogen outlet.
 26. The engine of claim 20 wherein atleast one of said compressors is oriented between said air inlet andsaid air separator, raising a pressure of the air; wherein at least oneintercooler is oriented between a first said compressor and said airseparator, each said intercooler reducing a temperature of the airpassing there through; wherein said air separator includes an expanderdownstream from a last said intercooler, said expander reducing apressure of the air and a temperature of the air to below a condensationpoint of the oxygen within the air, said air separator including saidoxygen enriched air outlet substantially free of nitrogen; wherein saidair separator includes a nitrogen outlet, and wherein said engineincludes a heat transfer device including means to transfer heat betweennitrogen exiting said air separator through said nitrogen outlet and airbetween said expander and said air inlet; wherein said expander iscoupled to an oxygen compressor interposed between said oxygen outlet ofsaid air separator and said combustion device, whereby a pressure of theoxygen is increased; wherein a scrubber is provided between said airseparator and said air inlet to remove gases capable of freezing fromthe air; and wherein said air separator includes a two column rectifierdownstream from said expander, said rectifier including said oxygenenriched air outlet and said nitrogen outlet.
 27. The engine of claim 14wherein said fuel is a hydrocarbon fuel including hydrogen, carbon andpossibly oxygen.
 28. The engine of claim 27 wherein said fuel and saidoxygen are provided at a stoichiometric ratio needed to produce saidcombustion products including substantially only steam and carbondioxide.
 29. The engine of claim 14 wherein at least a portion of saidcombustion products exiting said exhaust of said combustion productexpansion device are routed to a condenser where the steam within saidcombustion products is condensed to water, said condenser including afirst return duct to said water inlet of said combustion device, wherebythe steam/water acts as a working fluid for a Rankine cycle; whereinsaid condenser includes a heat transfer fluid therein for removal ofheat from the steam, said heat transfer fluid in fluid communicationwith an interior of a radiator oriented in the environment surroundingsaid engine with air from the surrounding environment passing against anexterior of said radiator and cooling said heat transfer fluid therein;and wherein said condenser includes a second outlet water duct sprayingwater into the surrounding environment and against said exterior of saidradiator for evaporative cooling of said heat transfer fluid within saidradiator.
 30. The engine of claim 14 wherein said reheater receives thecombustion products therein, a fuel therein and oxygen therein, andcombusts the fuel with the oxygen to enhance a temperature of thecombustion products therein.
 31. The engine of claim 30 wherein thecombustion products are mixed with reheater products of combustion ofthe fuel with the oxygen.
 32. The engine of claim 30 wherein at least aportion of the fuel received by the reheater is from said source offuel.
 33. The engine of claim 30 wherein at least a portion of theoxygen received by the reheater is from said oxygen enriched air outletof said air separator.
 34. The engine of claim 30 wherein a secondexpander is located downstream from said reheater and expands a fluidincluding the combustion products received by said reheater and thereheater products of combustion.
 35. A combustion engine providing cleanpower for various applications and featuring low NO_(x) production,comprising in combination: a source of air, the air including nitrogenand oxygen; a source of fuel, the fuel including hydrogen; means toremove at least a portion of the nitrogen from the air entering saidinlet so that the air exiting through an oxygen enriched air outlet isoxygen enriched; a fuel combustor, said fuel combustor receiving fuelfrom said source of fuel and air from said oxygen enriched air outlet,said combustor combusting the fuel with the air to produce elevatedpressure and elevated temperature combustion products including steam,the combustor having a discharge for the combustion products; acombustion products expander coupled to said discharge of saidcombustor, said combustion products expander outputting power from saidengine; means to remove at least part of a non-steam portion of thecombustion products from the combustion products after discharge fromsaid combustor, so that the combustion products have more steam than thecombustion products at said discharge; and means to return at least aportion of the steam rich combustion products back to said combustor.36. The engine of claim 35 wherein a reheater is located downstream ofsaid combustion product expander, said reheater enhancing a temperatureof said combustion products exiting said combustion product expander.37. The engine of claim 36 wherein a second combustion product expanderis located downstream of said reheater.